<!DOCTYPE html>
<html lang='en'>

<head>
    <meta charset='UTF-8'>
    <meta http-equiv='X-UA-Compatible' content='IE=edge'>
    <meta name='viewport' content='width=device-width, initial-scale=1.0'>
    <title>Document</title>
    <script src='../../vue.js'></script>
</head>

<body>
    <div id='app'>
        <button @click="isHot= !isHot">修改天气</button>
        <button @click="person.age++">修改年龄</button>
        <h1>{{person.age}}</h1>
        <h1>今天的天气真{{isHot?'热啊':'冷啊'}}</h1>
        <img :src="url" alt="">
    </div>
    <script>
        Vue.config.productionTip = false;
        const vm = new Vue({
            el: '#app',
            data() {
                return {
                    isHot:true,
                    url:'',
                    person:{
                        name:'老八',
                        age:34
                    }
                }
            },
            watch:{
                isHot:{
                    immediate:true,
                    handler(newValue){
                        this.url=newValue?'./re.webp':'./leng.gif'
                    }
                },
                person:{
                    deep:true,
                    handler(newValue){
                        alert('你老了')
                    }
                }
            }
        })
    </script>
</body>

</html>